1. Field of the Invention
The present invention relates, in general, to concrete form systems. More particularly, the present invention relates to a gang form having an improved insert for use with a concrete form system and a method of building the gang form.
2. Statement of the Problem
It is well-known in the construction industry to use concrete form systems to provide forms for pouring concrete in desired shapes, such as walls, stairs, sides of tanks, etc. Such concrete form systems often are made of a plurality of gang forms. A gang form conventionally is made of several form panels attached together at their edges until a surface of the desired dimensions is achieved. The form panels may be made of wood, metal, or other substances that provide the requisite flat surface and strength to bear the load placed on them by the poured concrete. However, most conventional form panels today are made of metal, preferably, aluminum, and are quite expensive. Therefore, it is advantageous to be able to reuse the form panels in a subsequent concrete building project.
To build concrete walls, the gang forms are generally positioned in a horizontally spaced relationship and interconnected with tie rods extending between the gang forms. After the concrete is poured and has hardened, the gang forms are removed.
The form panels from which gang forms are made are generally attached together at their edges with wedge bolts passing through holes in flanges surrounding each form panel. Wedge bolts are conventionally bolts with a slot in the body of the bolt. The bolt is inserted through the holes in the flanges, and a wedge is then inserted into the slot in the bolt and tapped into place. These wedges often loosen and fall out when the gang form is moved from place to place, causing the bolts to become loose and the gang form to lose structural integrity. Further, using such wedge bolts means that many small pieces must be available to the construction crew in order to replace lost wedges and bolts. In addition, one or more persons are needed to hold the form panels in place while yet another person inserts and wedges the wedge bolts. This causes difficulties during construction when it is preferable to have a minimum number of workers at a site.
The conventional form panels used for gang forms in concrete form systems generally include openings in the panels or in the flanges through which tie rods are received so that the gang forms can be interconnected to provide the concrete form system desired. The tie rods are generally attached to the form panels with a locking device, such as a cotter pin that passes through a hole in each end of the tie rod. Such a system for attaching the tie rods again has many small parts (the locking devices) which are easily misplaced and lost at a construction site. In order to position the tie rods, at least two persons must be present, one to insert and hold the tie rod in the opening and the other to attach the lock device to the tie rod. This system also limits the type of tie rod that can be used, as the tie rod is not directly attached to the form panel, which allows the form panel to slip along the tie rod. This is generally prevented by using tie rods with stops on the side of the form panel that faces the opposing form panel. It would be an advantage to be able to use other types of tie rods so that the same gang forms can be used in different types of construction projects.
The forces generated by the concrete as it is poured into the concrete form system are concentrated at the locations of the tie rods. These loads on the tie rods may cause the form panels to bend or break at those locations where the tie rods pass through the form panels, damaging the expensive form panels. In order to withstand these loading forces, the form panels are often reinforced at the locations of the tie rod openings. This necessarily adds to the cost and weight of the form panels. Often the gang forms must be additionally braced to stand up to the concrete loads. This means that more openings must be made in the gang forms in order to attach the braces.
When constructing a concrete wall, it is often advantageous to provide a scaffold on the gang form for the construction workers to stand on when they are directing the pouring of the concrete into the space between the gang forms or for other reasons. In order to attach a scaffold to a conventional form panel, the form panel must include either additional openings or additional brackets to permit the scaffold to be attached. Additional openings will tend to weaken the form panels and also provide places where concrete may leak through. Additional brackets add weight and expense to the form panels.
Thus, it would be advantageous in a concrete form system to provide a gang form that can be built by one person. It would also be advantageous to provide a gang form having a minimum of loose parts and a minimum of openings in the form panels. A gang form that can withstand the load forces placed on its tie rods by the concrete without additional bracing or strengthening of the form panels is needed Further, it would be desirable to provide a gang form that enables additional bracing and scaffolding to be removably attached without weakening the form panel with additional holes, or adding material to the form panel, thus raising its expense. Finally, a gang form that is easily reused from one construction project to the next would significantly reduce the costs of labor and materials.
A search of the prior art in which gang forms are used in concrete form systems discovered the following patents:
______________________________________ Williams 4,1551,975 May 1, 1979 Durbin 4,192,481 Mar. 11, 1980 Durbin 4,254,932 Mar. 10, 1981 Slonimsky et al. 4,811,927 Mar. 14, 1989 Reiner Oct. 19, 1943 Gallis et al. 4,473,209 Sep. 25, 1984 Johanson et al. 4,211,385 July 8, 1980 ______________________________________
U.S. Pat. No. 4,151,975 issued to Williams set forth a panel junction assembly in which wall form panels with flanges along adjacent edges are joined by a channel strip traversed by tie systems securing opposite panel assemblies. Securing bolts traverse the adjacent flanges and the walls of the channel strip, and the tie systems are cross pinned to the channel strip.
U.S. Pat. Nos. 4,192,481 and 4,245,932 to Durbin disclose a concrete wall form including a support structure comprising a beam capable of functioning as a stringer with an associated tie rod locking system.
U.S. Pat. No. 4,811,927 to Slonimsky et al. teaches a tubular panel connecting member for use with tie rods and panels for a concrete forming structure. The tubular connecting member has two flanges having slots within to receive bolts. Aligned holes are provided in the tubular connecting member for passage of tie rods.
U.S. Pat. No. 2,332,166 to Reiner sets forth a form for making concrete walls that includes a series of panels that are separated by strips placed between the panels. The strips engage the undercut edges of the panels and are held in place with a complex system of devices attached to keyhole slots in the panels.
U.S. Pat. No. 4,473,209 to Gallis et al. discloses a prefabricated modular wallform unit in which the panels are designed to mate against one another and to define an aperture through which a tie rod passes. The panels have flanges that are designed to be attached together with a T-bolt.
U.S. Pat. No. 4,211,385 to Johanson et al. shows concrete forms each including a plurality of rectangular panels secured edgewise together by connectors. Each connector includes a pair of half sleeves through with tie rods extend.
None of the above-described patents provides a gang form that solves the problems discussed above.
3. Solution to the Problem. The present invention provides a reusable gang form for use with a concrete form system. The gang form includes at least two form panels with flanges. An improved insert, preferably usable with conventional form panels, is positioned between the flanges of at least two adjacent form panels and is attached to the flanges with attachment devices, preferably bolts and nuts, that provide a secure and firm attachment that is not likely to be loosened during the movement or use of the gang form.
The tie rods that interconnect the gang forms are preferably attached to the improved insert. The improved insert has at least one lock member rotatably attached to one side of the insert to secure a tie rod. Because the lock member is attached to the insert before the insert is positioned in the gang form, there is no need for the builder to find and attach a separate lock device to secure the tie rods. Thus, there is no risk that lock members will be lost or attached incorrectly, for example, in the wrong locations on the insert so that the tie rods are only attachable at one end, or attached insecurely. In a concrete form system having a plurality of gang forms of the present invention, one person can easily place the tie rods through the openings in the inserts and lock the tie rods in place.
The gang form of the present invention can be built by one person.
It is an object of the present invention to provide an improved insert that can be positioned between conventional form panels to provide a gang form for use in a concrete form system.
It is another object of the present invention to provide a gang form that has a minimum of unattached or loose parts.
It is an object of the present invention to provide an improved insert that has a lock member attached.
It is another object of the present invention to provide a method by which gang forms are built by one person.
It is yet another object of the present invention to provide a pick-up member that is retractable when not being used.